package com.cnsugar.common.jdbc.dialect.db;

import com.cnsugar.common.jdbc.dialect.Dialect;

/**
 * 
 * Mysql方言的实现
 * 
 * @Author Sugar
 * @Version 2017年3月30日 下午6:35:20
 * @since JDK 1.5
 */
public class MySQLDialect implements Dialect {
	public final static String NAME = "MySQL";
	private static MySQLDialect instance;

	private MySQLDialect() {
	}

	public static MySQLDialect getInstance() {
		if (instance == null) {
			instance = new MySQLDialect();
		}
		return instance;
	}

	@Override
	public String getLimitString(String sql, int offset, int limit) {
		return getLimitString(sql, offset, Integer.toString(offset), Integer.toString(limit));
	}

	public boolean supportsLimit() {
		return true;
	}

	/**
	 * 将sql变成分页sql语句,提供将offset及limit使用占位符号(placeholder)替换.
	 * 
	 * <pre>
	 * 如mysql
	 * dialect.getLimitString("select * from user", 12, ":offset",0,":limit") 将返回
	 * select * from user limit :offset,:limit
	 * </pre>
	 *
	 * @param sql
	 *            实际SQL语句
	 * @param offset
	 *            分页开始纪录条数
	 * @param offsetPlaceholder
	 *            分页开始纪录条数－占位符号
	 * @param limitPlaceholder
	 *            分页纪录条数占位符号
	 * @return 包含占位符的分页sql
	 */
	public String getLimitString(String sql, int offset, String offsetPlaceholder, String limitPlaceholder) {
		StringBuilder stringBuilder = new StringBuilder(sql);
		stringBuilder.append(" LIMIT ");
		if (offset > 0) {
			stringBuilder.append(offsetPlaceholder).append(",").append(limitPlaceholder);
		} else {
			stringBuilder.append(limitPlaceholder);
		}
		return stringBuilder.toString();
	}

	@Override
	public String getDatabseProductName() {
		return NAME;
	}

	@Override
	public String getMark() {
		return "`";
	}
}
